The present invention relates to catalysts for the polymerization of ethylene and to a process for their preparation.
French Pat. No. 2,324,652 describes solid catalysts for polymerizing ethylene and/or .alpha.-olefins, wherein the catalysts include compounds containing titanium, magnesium, and halogens and in which the atomic ration of the halogen, X, to magnesium, Mg, is not less than 1(X/Mg.gtoreq.1) and the atomic ratio of the titanium, Ti, to magnesium is greater than 1(Ti/Mg&gt;1). A catalyst of this type can be obtained by bringing a titanium compound into contact with the solid halogenation product obtained from reacting a halogenating agent with a magnesium compound, such as a magensium alcoholate. During the halogenation reaction, the atomic ratio of halogen to magnesium is greater than 2; X/Mg&gt;2.
European Pat. No. 7,565 describes the preparation of a titanium compound for the manufacture of catalysts for the polymerization of .alpha.-olefins, which comprises reacting a magnesium alcoholate with benzoyl chloride in a mill, the ethyl benzoate formed being retained in the product obtained, and then in treating the product twice with an excess of titanium tetrachloride.